The Laboratory of Neurobiology of the Medical Sciences Campus of the University of Puerto Rico is an interdepartmental research facility, which offers both to U.P.R. and visiting scientists and students the environment and equipment necessary to conduct research projects on the morphology (including ultrastucture), electrical activity and pharmacological sensitivity of excitable cells and tissues. The collecting facilities of the Laboratory of Neurobiology offer access to the rich Caribbean marine fauna as well as to the many scientifically interesting invertebrate and plant species of the rain forests of this island. Present projects include: I. Regulation and axonal transport of Na,K-ATPase; II. Comparative aspects of excitation phenomena: a) Central connections and functional significance of the spine nerves of Diadema, b) Mechanical and pharmacological properties of the spine ligaments in sea urchin, c) Ultrastructure and properties of the dorsal fin muscle of Hippocampus, d) Excitation-contraction coupling in Ascaris esophagus; III. a) Characterization of muscle membrane receptors in Sabellastarte, b) Actions of ciguatoxin on animal cells; IV. Modulation of cholinergic receptors by succinylated derivatives of buffer TES; V. Anatomical basis of color vision in ground squirrels; VI. Kinetic and pharmacological properties of calcium channels activated by sulfhydryl reagents in crustacean muscle.